Safety flare

ABSTRACT

A safety flare for burning combustible gas without smoke or a luminous flame including a vertical stack the top of which is surrounded by an open-topped housing spaced from the stack and having means to introduce a non-flammable gas into the space between the stack and the housing in the manner to produce a swirling flow around the open end of the stack.

United States Eatent Simpson et al.

[ 51 Feb. 25, 1975 SAFETY FLARE Inventors: Samuel W. Simpson, Florissant,

Mo.; Thomas E. Innocenzi, Houston, Tex.

Assignee: Shell Oil Company, New York, N.Y.

Filed: Jan. 22, 1973 Appl. No.: 325,474

Related U.S. Application Data Continuation of Ser. No. 101,229, Dec. 24, 1970, abandoned,

U.S. Cl 431/4, 431/9, 431/202, 431/353 lnt. Cl F23j 7/00 Field of Search 431/4, 5, 9, 90, 353, 354, 431/182, 202, 163; 23/277 C; 110/8 A; 239/405, 406

References Cited UNITED STATES PATENTS Neff 23/277 C 733,463 7/1903 Dennison 431/163 1,369,602 2/1921 Amsler 239/406 2,506,972 5/1950 Schellentrager e a1. 431/202 2,779,399 1/1957 Zihk et a1. 431/5 X 3,219,418 11/1965 Witmire 23/277 C 3,240,433 3/1966 Keating 239/405 K 3,567,399 3/1971 Altmann et a1. 431/5 Primary Examiner-Carroll B. Dority, Jr. Attorney, Agent, or Firm-A. A. Jecminek [57] ABSTRACT A safety flare for burning combustible gas without smoke or a luminous flame including a vertical stack the top of which is surrounded by an open-topped housing spaced from the stack and having means to introduce a non-flammable gas into the space between the stack and the housing in the manner to produce a swirling flow around the open end of the stack.

1 Claim, 3 Drawing Figures All SAFETY FLARE This is a continuation of application Ser. No. 101,229, filed Dec. 24, 1970 and now abandoned.

BACKGROUND In many industrial processes, particularly in refining petroleum, large quantities of waste combustible gas is produced. This waste gas must be disposed of safely and without polluting the atmosphere. Additionally, emergency situations frequently produce large flows of material that must also be safely disposed of, for example, when high pressure equipment must be quickly depressurized through an emergency pressure relief system. To provide a means for safely disposing of such materials it is common to employ safety flares which are generally vertical stacks erected at a safe location and piped so that waste gas or gas which must be disposed of in an emergency situation can be introduced into the flare, ignited, and burned harmlessly well above the ground level.

Safety flares present severe problems in several respects. Safety flares must be constructed so that they can dispose of various gases, in a refinery ranging from hydrogen to oils in character. Additionally, the gases to be disposed of in safety flares vary widely in quantity, ranging from a small continuous flow of waste gas to tremendous surges when high pressure equipment must be quickly depressurized. The flares also produce problems with the environment because, in avoiding pollution of the atmosphere by burning dangerous gases they produce smoke and luminous flames that may disturb the immediate vicinity, and loud noises when large quantities of gas are being burned.

THE INVENTION This invention provides a novel flare construction which is capable of disposing of widely varying amounts of combustible gas with a smokeless, nonluminous flame and a greatly abated production of noise. The flare of this invention includes a vertical stack having conventional means for supplying it with the combustible gases to be disposed of. The stack is surrounded at its upper end with a housing and the housing is characterized by having an open upper end that extends above the upper end of the stack, by being spaced from the stack, and sealed at its lower end to the side of the stack. The housing has means for introducing a non-flammable gas into the space between the housing and the stack in such a manner to produce a swirling gas stream around the top of the stack. The flare also includes conventional means for igniting waste gas.

Although, within the broad terms of this invention many structural variations are possible, typically the.

apparatus of this invention consists of a cylindrical stack surrounded around its upper opening with a coaxial cylindrical or inverted truncated conical housing having a tangential steam line entering the cylindrical or conical wall of the housing at a point slightly below the upper end of the stack.

Although it is not definitely known and it is not intended to limit this invention by the following explanation, it is thought that the beneficial operation of the safety flare of this invention is obtained through the following operation. Luminous, smoky flames are due to incomplete mixing of air and combustible gas, and the noise of a safety flare is thought to be due to the abrupt collision of high velocity gas with the relatively quiet air above the flare. It is thought that the flare of this invention operates to alleviate noise, smoke, and luminous flame by producing a mixture of air and combustible gas prior to the burning. The swirling gas within the housing produces a low pressure vortex into which air is drawn, and the turbulence within the housing results in good and intimate mixing of the air and the fuel before it is burned. As a result, when combustion finally takes place it is in the form of a blue, virtually invisible flame that will not disturb the surrounding area either during the day or during the night. The well mixed airfuel mixture also is burned completely thereby completely eliminating smoke. Forming the combustible gas into a swirling cylinder provides a greatly enlarged surface for air and combustible gas to come in contact with one another, and the air being drawn into the vortex enters the combustible gas as a rapidly moving stream which diminishes the impact effect of the combustible gas and the air with a concommitant reduction of noise. The operation of the flare of this invention as compared with conventional flares indicates that the flare of this invention substantially eliminates the problems of smoke and luminous flames, and greatly diminishes the noise produced in burning a given quantity of combustible gas.

As indicated above, a suitable safety flare must accept widely varying loads of combustible gas. It has been found that the amount of swirling noncombustible gas introduced into the housing preferably is varied corresponding to the amount of combustible gas that is to be burned. It is a preferred embodiment of this invention to vary the amount of swirling noncombustible gas by measuring the quantity of combustible gas entering the stack and adjusting the amount of non-combustible gas introduced into the housing as a swirling gas stream in direct response to the amount of combustible gas to be disposed of.

The invention may be best explained with reference to the accompanying drawing wherein:

FIG. 1 is an illustration in sectional elevation view of the top portion of a flare embodying this invention;

FIG. 2 is a plan view of the flare of FIG. 1; and

FIG. 3 is a highly schematic flow diagram illustrating the relationship of various parts of the flare and one control means that may be employed.

In FIGS. 1 and 2, a vertical stack 10 extending a sufficient height above the ground for purposes of safety terminates in an open end 11. The top of the stack 10 is surrounded with a housing 12, illustrated herein asan. inverted truncated cone that is coaxial with the stack 10. The housing 12 has an open top portion 13 and a lower enclosed portion 14 that seals the housing .12 against the wall of the stack 10. A line 15 carrying a non-combustible gas enters the housing 12 tangentially at the opening 16. It has been found that the housing 12 may be cylindrical or conical and is preferably conical with the side walls having an angle to vertical of less than 10, preferably about 5. It has also been found that the line 15 may operate to introduce noncombustible gas at any angle, but preferably introduces the non-combustible gas at an angle so that it discharges upwardly within the housing 12 at an angle of 15 or less, preferably at an angle between l0 and 15 to the horizontal. It is also preferred that the opening 16 be below the upper opening 1] of the stack 10 in orderto ensure that the opening 11 is surrounded by a swirling gas stream. It is, of course, evident that more than one inlet for non-combustible gas may be employed. It is also evident that a spark plug or other conventional igniter will be used although none is shown.

FIG. 3 illustrates schematically a flow diagram of one method for employing the stack of this invention. In FIG. 3 the stack extends vertically above grade and the upper portion thereof is surrounded by housing 21. Steam is introduced tangentially into housing 21 through line 22. Lines 23, of pressure that provide gas 25 and 26 represent sources of waste gas or connections for emergency relief of pressure that prpovide gas to be disposed of in the flare of this invention. All of the gas sources discharge into a common line 27 which enters the bottom of stack 20 first passing through indicator 28 which is a suitable device for measuring the flow of combustible gas. The measuring device 28 is typically a Venturi meter although any suitable flow measuring device may be employed. It is preferred to have the metering device 28 close to the bottom of stack 20 so that the downstream pressure from measuring device 28 is relatively constant. Means 29 is provided to open and close valve 30 in steam line 22 responsive to changes in the flow rate sensed by means 28. Thus, with the arrangement illustrated in FIG. 3, the amount of incombustible gas producing the swirling motion within housing 21 may be directly related to the amount of combustible gas that is to be disposed of through the The non-combustible gases that may be employed in this invention include but are not limited to steam, nitrogen, air, carbondioxide and. others. In addition to providing a swirling gas stream and to producing a vortex, it has been found that the swirling incombustible gas insulates the housing 12 from direct contact with flames and thereby prevents its destruction. Although illustrated as a tangential inlet, the incombu'stible gas may be introduced into the housing by other means that will produce a swirling gas stream within the housing.

What is claimed is:

1. A process for flaring combustible gas into the air which comprises:

a. passing combustible gas upwardly through an open-topped cylindrical stack and into an enlarged coaxial housing extending above the top of the stack;

b. passing steam into the housing in a manner to produce a swirling mixture of combustible gas and steam and creating a low-pressure vortex into which air is drawn;

c. igniting the resultant swirling mixture with resultant improved combustion and reduced noise level and d. discharging the resultant burning gas mixture into the atmosphere. 

1. A process for flaring combustible gas into the air which comprises: a. passing combustible gas upwardly through an open-topped cylindrical stack and into an enlarged coaxial housing extending above the top of the stack; b. passing steam into the housing in a manner to produce a swirling mixture of combustible gas and steam and creating a low-pressure vortex into which air is drawn; c. igniting the resultant swirling mixture with resultant improved combustion and reduced noise level and d. discharging the resultant burning gas mixture into the atmosphere. 